Analysis of Changes in SUMO-2/3 Modification during Breast Cancer Progression and Metastasis

SUMOylation
is an essential posttranslational modification and
regulates many cellular processes. Dysregulation of SUMOylation plays
a critical role in metastasis, yet how its perturbation affects this
lethal process of cancer is not well understood. We found that SUMO-2/3
modification is greatly up-regulated in metastatic breast cancer cells
compared with nonmetastatic control cells. To identify proteins differentially
modified by SUMO-2/3 between metastatic and nonmetastatic cells, we
established a method in which endogenous SUMO-2/3 conjugates are labeled
by stable isotope labeling by amino acids in cell culture (SILAC),
immunopurified by SUMO-2/3 monoclonal antibodies and epitope–peptide
elution, and analyzed by quantitative mass spectrometry. We identified
66 putative SUMO-2/3-conjugated proteins, of which 15 proteins show
a significant increase/decrease in SUMO-2/3 modification in metastatic
cells. Targets with altered SUMOylation are involved in cell cycle,
migration, inflammation, glycolysis, gene expression, and SUMO/ubiquitin
pathways, suggesting that perturbations of SUMO-2/3 modification might
contribute to metastasis by affecting these processes. Consistent
with this, up-regulation of PML SUMO-2/3 modification corresponds
to an increased number of PML nuclear bodies (PML-NBs) in metastatic
cells, whereas up-regulation of global SUMO-2/3 modification promotes
3D cell migration. Our findings provide a foundation for further investigating
the effects of SUMOylation on breast cancer progression and metastasis.